This invention relates to making bearings with low friction surfaces and metal backing members.
Bearings are well known which comprise rigid support members to which low friction materials defining the bearing surface are attached. Bearing surfaces are often made from various compositions, including thermoplastic resins, especially Teflon (trademark of DuPont for polytetrafluoroethylene). The following U.S. patents teach various plastic bearing compositions.
______________________________________ Inventor U.S. Pat. No. ______________________________________ White 3,037,893 ______________________________________ Dodson & White 3,455,864 Ikeda & Kawakita 3,779,918 Cairns & Walton 3,781,205 Cairns 3,879,301 Nienart, Sanders & Jeges 3,908,038 Ikeda & Ishikawa 3,985,661 Cairns 3,994,814 ______________________________________
Bearings with such surfaces often have metal backings to provide strength, rigidity, and shape. A continuing problem has been to find a way to form the bearing and to simply yet satisfactorily fasten the low friction surface material to the metal backing. Such low friction materials have been molded, sintered, glued, sewn, and clipped on to bearing backings. Sometimes low friction material is knit or woven into a fabric and then attached to backing elements. U.S. Pat. No. 3,464,845 to Osborn and Gobran, U.S. Pat. No. 3,037,893 to White and U.S. Pat. No. Re. 24,765 to White are examples of the use of low friction fabric.
A disadvantage of prior art processes for making low friction bearings, other than simple flat bearings, is the frequent need for specialized and complex methods such as molding and sintering for bonding low friction materials to backings and for forming the bearings.
Another disadvantage of the prior art processes for making low friction bearings is that, when relatively simple methods are used, the resulting bearing often has a seam on the bearing face. For example, U.S. Pat. No. 3,848,306, to Morse, discloses a method for making a cylindrical bearing in which a flat layer of plastic and a layer of perforated metal are bonded together to form a single sheet, which is then bent and swaged into a cylindrical tube. The resulting bearing has a seam. Other examples of bearings with seamed surfaces are U.S. Pat. No. 3,881,791 to Hentschel, U.S. Pat. No. 3,252,346 to Prior, and U.S. Pat. No. 3,033,623 to Thomson.
Another shortcoming of the prior art is the time required by the use of separate, sequential steps for bonding low friction material to metal backings and for forming the bearing backings into the final configuration of the bearing.